Magnetic recording and playing of a magnetic signal in a flexible magnetic disc comprising a sheet in a jacket, involving connecting a sheet-position determining part of a writing and/or reading apparatus to a central aperture of the jacket and sheet, and rotating the sheet, is known, and the magnetic disc is commonly called a "floppy disc". For the sheet to be stored in the jacket, a space is provided in the magnetic disc which is slightly larger than the sheet, and thus the sheet sometimes moves to an eccentric position in the jacket during use or storage, with the result that the central aperture of the sheet deviates from the position of a position-determining part (collet) of the apparatus when the disc is loaded on the apparatus, and the sheet may be supported at an eccentric position at the position determing time.
FIG. 1A and FIG. 1B illustrate this type of flexible magnetic sheet, located in a rectangular jacket 1 having circular open part 1a, with circular flexible magnetic sheet 2 having central aperture 2a thereof exposed in the afore-mentioned central circular open part 1a, said sheet being stored in the jacket to allow free rotation.
Upon loading this flexible magnetic disc on the writing and/or reading apparatus, rotating part 3 (see FIGS. 2-4) of the position-determing part is fitted from under part of the sheet 2, and collet 4 is lowered from upper part of the sheet and is brought into the circular concave part 3a of rotating part 3 as shown in FIG. 2. At this time, the edge of central aperture 2a does not always correspond to the position of circular concave part 3a of rotating part 3, and is many times out of proper alignment. If collet 4 is lowered in this state, some part of the portion surrounding the edge of aperture 2a of the sheet 2 may be pinched between collet 4 and concave part 3a of rotating part 3, such that the sheet rotates eccentrically. As writing and reading cannot be carried out correctly unless magnetic disc sheet 2 rotates while being correctly centered corresponding to the central rotating axis, such eccentric pinching should very desirably be prevented. Moreover, there exists another problem, viz., that rattling occurs during rotation due to the absence of planarity of the sheet 2 when it is supported and rotated under such an eccentric pinched state.
Upon connecting the sheet 2 by lowering the collet 4, it is necessary that the portion surrounding the edge of the central aperture of the sheet possesses an appropriate hardness, and that the friction coefficient (.mu.) between the sheet 2 and collet 4 as well as between the sheet 2 and rotating part 3 is small, in order that the sheet 2 is loaded correctly as shown in FIG. 4, not as shown in FIG. 3.
It has been proposed to adhere an annular reinforcement member (ring) concentrically arranged adjacent central aperture of the disc sheet, as described in U.S. Pat. No. 4,052,750, in order to overcome such problems. However, this method has a problem in that an adhesive comes out and the collet stains where the sheet is used for a long period of time, resulting in incorrect writing and reading.
It has been known that a UV (ultraviolet ray) hardenable resin can be applied to a surface of a disc sheet around the central aperture by a tampon printing method, and then hardened to provide a protective layer, as described in U.S. Pat. No. 4,387,114. This protective layer formed by the UV hardening resin does not involve the problem that an adhesive comes out therefrom, but the method requires two step printing operations, and printing accuracy is low.